In battery powered electrical equipment, remaining battery capacity can be detected and displayed to certify a term of energizing the equipment. There is other equipment in which an energy saving mode or usual mode can be selected to prolong the term of energizing the equipment. In this equipment, an operator has to operate some keys. Furthermore, it is necessary to operate some keys to insure a current energy saving mode. In this case, the displayed current energy saving mode has no relation to the displayed remaining battery capacity. That is why it is difficult to confirm that an appropriate energy saving mode is selected in accordance with the remaining battery capacity by the contents of displayed information. Furthermore, while executing data processing in a normal energy saving mode, the equipment sometimes goes down and important data are lost as a result of loss of the battery power.
Even if the remaining battery capacity and the selected battery energy mode are displayed simultaneously, it is difficult for an operator to select an appropriate mode for desired operating time.